How do I tunnel subversion over ssh?

Okay folks, here's the scenario:

I keep most of my course work in a subversion repository, because I tend to hammer away at it from different machines and the merge facility makes life a lot easier. At the moment I bring my laptop home, update and commit any changes, and go away again. It's actually become a great way of working. My laptop becomes my ~ away from ~, and the headaches are surprisingly few and far between.

It can be a little messy though, especially when I get into work and I realise I haven't merged everything I'd like to. I'd also like to be able to do a similar thing from other machines around the place. What I need to be able to do is update and commit over the internet. However, I don't want to expose svnserve to the internet if possible. The only service I have open to the big bad world is ssh, and I'd like to keep it that way.

So my question is --- is it possible to tunnel svn via ssh? If so, how?